The present invention relates to the use of magnetic tag elements to locate concealed inanimate objects to which such tags are attached. Such inanimate objects should be understood to include movable objects, such as surgical instruments and other medical treatment devices which must be positioned and controlled within a living body during medical treatment, as well as fixed objects which may need to be located, such as buried sewer pipes and fiber-optic cables. The invention also relates to the provision of medical treatments with treatment devices which are concealed within a living body.
The invention relates to a system of tagging, as well as the means and method for finding, locating and/or tracking preferably nonmagnetic objects. Examples of the application include: tracking of medical diagnostic, surgical or therapeutic tools used on or within a human or animal body, determining the location of hidden objects such as land-mines, buried fiber-optic cables or plastic plumbing pipes, determining the position of an object subjected to computer or automated control, locating errant golf-balls.
There are numerous instances where it is important to locate an object out of visual contact or where monitoring the movement of an invasive object such as a catheter is required in order to know for example, where the tip of the catheter is located. While much of this can be done using MRI or x-ray techniques, the equipment and its use for such monitoring is expensive and somewhat cumbersome. Furthermore, the extensive use of x-rays for monitoring objects within humans is to be avoided whenever possible for health reasons. It therefore becomes preferable to be able to monitor such hidden objects by methods that are easy to utilize and which at the same time give a very accurate position of the object. In addition, a large signal to noise ratio is desirable.
Broadly, the present invention provides a system for determining the location of an inanimate object after attachment, to the object, of an element (or xe2x80x9ctagxe2x80x9d) comprising a magnetic material, the aforesaid system comprising:
a) an aforesaid element which is capable of emitting a non-linear magnetic signal in response to an applied ac magnetic field,
b) a magnetic field generator for irradiating the aforesaid element with an applied ac magnetic field,
c) a movable magnetic field sensor operable to detect the aforesaid non-linear magnetic signal from a plurality of selected mutually displaced positions to produce a corresponding plurality of element-locating signals, and
d) a computing apparatus for converting the aforesaid element-locating signals to a location image of the aforesaid object.
The invention also provides a method for determining the location of a concealed inanimate object, the method comprising the steps of:
a) attaching, to this object, an element comprising a magnetic material which is capable of emitting a non-linear magnetic signal in response to an applied ac magnetic field,
b) irradiating the aforesaid element with an applied ac magnetic field,
c) moving a magnetic field sensor in spaced adjacency to the aforesaid element to detect the aforesaid non-linear magnetic signal from a plurality of selected mutually displaced positions to represent a corresponding plurality of element-locating signals, and
d) converting the aforesaid element-locating signals to a location image of the aforesaid object.
Preferably, the aforesaid element comprises an amorphous magnetic material capable of emitting a non-linear magnetic signal which is characterized by Barkhausen jumps in response to the aforesaid applied ac magnetic field. Moreover, it is preferred that the aforesaid element (or xe2x80x9ctagxe2x80x9d) comprises an amorphous magnetic wire characterized by a magnetization which is reversible in direction in response to the aforesaid applied ac field, the magnitude of which may be selected as a function of the length or other dimension of the amorphous magnetic wire.
As will be understood, the aforesaid inanimate object, which is to be located, should preferably be non-magnetic and may take many different forms. For example, the object may be a medical treatment device such as a catheter, surgical instrument, brachytherapy tube, or therapeutic radiation device that is disposed within a living body, whether such object has merely been misplaced or needs to be controlled and manipulated while in its concealed position. Alternatively, the object may be a hidden underground sewer pipe, optical fiber cable, or even a valuable instrument that may be inadvertently buried during excavation. Other applications will be readily identifiable as well.
The invention also provides a system for providing medical treatment to a living body with a treatment device, the system comprising:
a) a treatment device disposed within said living body,
b) an element or xe2x80x9ctagxe2x80x9d (as described herein above) attached to the aforesaid treatment device, wherein this element comprises a magnetic material and is capable of emitting a non-linear magnetic signal in response to an applied ac magnetic field,
c) a magnetic field generator for irradiating the aforesaid element and a juxtaposed region of the living body with an applied ac magnetic field,
d) a movable magnetic field sensor operable to detect the aforesaid non-linear magnetic signal from a plurality of selected mutually displaced positions to produce a corresponding plurality of element-locating signals,
e) a computing apparatus for converting the aforesaid element-locating signals to a location image of the treatment device, and
f) a controller device for controlling the position and treatment action of the treatment device in synchronism with the aforesaid location image.
Preferably, the treatment device may be a catheter, surgical instrument, brachytherapy tube holding one or more radioactive particles, a therapeutic radiation emitting device, or the like.
The invention also provides a method for providing medical treatment to a living body with a treatment device concealed therein, comprising the steps of:
a) attaching, to the treatment device, an element (as described herein above) comprising a magnetic material, the aforesaid magnetic material being capable of emitting a non-linear magnetic signal in response to an applied ac magnetic field,
b) irradiating the aforesaid element with an applied ac magnetic field,
c) moving a magnetic field sensor in spaced adjacency to the aforesaid element to detect the aforesaid non-linear magnetic signal from a plurality of selected mutually displaced positions to represent a corresponding plurality of element-locating signals,
d) converting the aforesaid element-locating signals to a location image of the aforesaid treatment device, and
e) controlling the position and treatment action of the aforesaid treatment device in synchronism with the aforesaid location image.
The novelty of the present invention utilizes a sharp Barkhausen jump or sudden change in magnetization of an amorphous magnetic material attached to an object, the magnetic material acting as a locator or tag. A relatively high frequency magnetic signal compared to the frequency of an interrogating magnetic field is emitted by the magnetic element or tag. The wire which is utilized in the preferred embodiment has been developed by Unitika, Ltd., Kyoto, Japan. The wire is formed by a technique that uses a molten metal sprayed onto a cold water surface on a rotating wheel, a process referred to an xe2x80x9cin-rotating-water-quenched.xe2x80x9d This spin melting and rapid quenching results in an amorphous rather crystalline state of the resulting magnetic alloy. The magnetic signal resulting from the flux reversal in such a wire can be readily discriminated from the excitation signal because the wires""emitted magnetic frequency spectrum contains components that are several orders of magnitude higher than that of the excitation signal.
The use of such a wire as an implant onto a tumor to locate the position of the tumor during periods of radiation treatment is disclosed in co-pending U.S. patent application Ser. No. 09/241,506, entitled, xe2x80x9cIMAGING OF INTERNAL STRUCTURES OF LIVING BODIES BY SENSING IMPLANTED MAGNETIC DEVICES,xe2x80x9d filed Feb. 1, 1999, by von Gutfeld, et al.
The xe2x80x9clocating apparatusxe2x80x9d is comprised of two parts. The first component is a magnetic field generator or excitation coil which emits a low frequency ac magnetic field of intensity greater than xcx9c0.5-1 Oersteds in the region of the position of the locator tag, along the direction of the wire or foil. The second component consists of one or more movable magnetic field sensors or sensing coils to detect the emitted Barkhausen jumps or sudden changes in magnetic field arising from the locator tag under the influence of the field of the excitation coil.
The apparatus and method of search can be used in a variety of medical applications such as the tracking of a catheter within the body of a human or animal. More generically, one or more short lengths of wires can be attached along the lengths of plastic pipes or fiber optic cables to be buried and later located, or even attached to explosives such as land-mines, or golf balls, to enable their positions to be determined at a future time.